The present invention relates generally to the construction and configuration of electrical machines including motors and generators. More specifically, the invention relates to an AC electrical machine featuring increased efficiency and reduced size as a result of the elimination of iron core losses and winding losses by the strategic use of superconducting diamagnetic materials.
Traditionally, AC machines have used either permanent magnet rotors or DC excited wound rotors to produce a rotating magnetic field linking stator windings mounted about the rotor. The stator windings were themselves surrounded by a stator core. The stator core usually included teeth extending radially inward defining slots into which the stator windings would be placed. The air gap for these types of machines is defined as the distance between the surface of the rotor magnetic pole and the innermost portion of the stator core. The stator core provided a magnetic link between opposite magnetic poles on the rotor, with the only open sections of the magnetic link being those defined by the air gap. While the stator core and stator teeth were believed necessary to provide the magnetic link within electrical machines, the core is also a source of energy loss within the machine primarily in the form of hysteresis and eddy current losses.
With the introduction of high magnetic strength permanent magnets, it became possible to build electrical machines which have much larger magnetic air gaps and which have eliminated the stator teeth altogether, as for example J. Denk, U.S. Pat. No. 4,709,180 herein incorporated by reference. Additionally, losses associated with eddy currents within the stator core were reduced by the use of laminated disks of ferromagnetic material to construct the stator core. However, even with this construction, the losses associated with the stator core account for about 25% of the machines total losses, the remainder being copper winding losses, miscellaneous eddy current losses, bearing heat, and windage losses.
It is therefore apparent that in order to significantly improve he efficiency of electrical machines of this type, the losses associated with the stator core, the bearings, or the windings must be reduced.